Search

There is currently a great deal of interest in the use of nanoscale devices to emulate the behaviors of neurons and synapses and to facilitate brain-inspired computation. Here, it is shown that percolating networks of nanoparticles exhibit stochastic spiking behavior that is strikingly similar to that observed in biological neurons. The spiking rate can be controlled by the input stimulus, similar to "rate coding" in biology, and the distributions of times between events are log-normal, providing insights into the atomic-scale spiking mechanism. The stochasticity of the spiking behavior is then used for true random number generation, and the high quality of the generated random bit-streams is demonstrated, opening up promising routes toward integration of neuromorphic computing with secure information processing.

Financial industry in a developing country like India is undergoing through a very dynamic pace of restructuring; it is imperative for any bank to continuously monitor their efficiency by keeping p...

The central sulcus (CS) is a prominent landmark of the brain, separating the parietal lobe from the frontal lobe and the primary motor cortex from the primary somatosensory cortex. Variations in the morphology of the central sulcus are seen with respect to the length and depth of the central sulcus. This study was done to establish a normal standard of length and depth of central sulcus in different age and sex groups of Bangladeshi people. Interhemispheric age and gender differences of the central sulcus were done by cross sectional descriptive study which was performed into four categories- Group A (20 to 29 years), Group B (30 to 39 years), Group C (40 to 49 years) and Group D (50 yearsabove). The specimens were collected from morgue in the department of Forensic Medicine, Mymensingh Medical College, Bangladesh by purposive sampling technique. The length of central sulcus was measured by using thread and the depth was measured by using wooden stick at middle of the upper, middle and lower third of the central sulcus in superolateral surface. The mean length of central sulcus was 10.51±0.529cm to 9.78±0.996cm in male and 10.27±0.786cm to 8.83±0.379cm in female. Depth of the central sulcus was 1.333±0.100cm to 1.029±0.125cm in male and 1.173±0.144cm to 1.01±0.200cm in female. The difference in mean lengthdepth of the central sulcus for both left and right hemisphere between male and female was statistically non significant in all age groups. In present study the length and depth of the central sulcus showed gradual decreasing values with advancing age. Knowledge of morphometry of central sulcus is not only important during neurosurgery of brain but also holds tremendous significance in diagnosis and management of diseases of the cerebral cortex. The present study will help to increase the information pool on the length and depth of the central sulcus of Bangladeshi people which will minimize the dependency on foreign standards.

Placenta is the mirror of maternal and fetal status; it reflects the changes due to complications in pregnancy of mother. The growth and survival of the fetus in utero is directly related to formation, development and maturation of the placenta. Placental index was correlated to poor pregnancy outcomes. Placental index can help to identify fetal growth restriction which is result of placental insufficiency and is characterized by insufficient trasnsplacental transport of nutrients and oxygen. This cross sectional descriptive study would provide information about the ratio of placental index in different gestational age group in Bangladeshi women. To achieve this aim the study was performed on 60 human placenta and corresponding fetuses and gestational age (in weeks) categorized as Group A (28-32), Group B (33-37), Group C (38-40). These sample and information were collected from normal pregnancy in Gynecology and Obstetrics Department of Mymensingh Medical College Hospital from July 2009 to June 2010. After preservation in 10% formal saline, study was done in Department of Anatomy in Mymensingh Medical College. In this study, the mean±SD placental index was in Group A (0.187±0.113), Group B (0.153±0.025) and Group C (0.166±0.025) and also observed that mean placental index decreased with age up to certain level then increase in Group C. The mean placental index was maximum in Group A (0.187±0.113) and was minimum in Group B (0.153±0.025). The mean difference of placental index between Groups AB, AC and BC was statistically not significant. Observed findings of this study were compared with those of Western and Bangladeshi researches.

This cross sectional descriptive study was performed on 80 human placenta and umbilical cord to find out the variation in length of umbilical cord of healthy Bangladeshi mother in relation to different gestational age. This study was conducted in the Department of Anatomy, Mymensingh Medical College, Mymensingh, from January to December 2018. The specimens were collected from the Department of Gynaecology and Obstetrics, Mymensingh Medical College Hospital, Mymensingh, Bangladesh by purposive sampling technique. According to gestational age the collected samples were divided into three groups. They were Group A (28 to 36 weeks), Group B (37 to 40 weeks) and Group C (above 40 weeks) and examined morphologically by fine dissection method. The length of umbilical cord was measured with the help of flexible tape in cm. For statistical analysis, differences of length between age groups were analyzed by using unpaired student 't' test. The mean±SD length of umbilical cord was 56.15±7.61cm in Group A, 62.54±8.78cm in Group B and 68.54±10.53cm in Group C. It was also observed that the mean length of the umbilical cord was increased with increase of gestational age. The mean difference of length of umbilical cord between Groups A and C was statistically highly significant (p0.001), difference between Groups A and B was statistically moderately significant (p0.01) but the difference between Groups B and C was statistically significant (p0.05). This study was done to provide information about the length of umbilical cord in different gestational ages of healthy pregnancies.

Self-assembled networks of nanoparticles and nanowires have recently emerged as promising systems for brain-like computation. Here, we focus on percolating networks of nanoparticles which exhibit brain-like dynamics. We use a combination of experiments and simulations to show that the brain-like network dynamics emerge from atomic-scale switching dynamics inside tunnel gaps that are distributed throughout the network. The atomic-scale dynamics emulate leaky integrate and fire (LIF) mechanisms in biological neurons, leading to the generation of critical avalanches of signals. These avalanches are quantitatively the same as those observed in cortical tissue and are signatures of the correlations that are required for computation. We show that the avalanches are associated with dynamical restructuring of the networks which self-tune to balanced states consistent with self-organized criticality. Our simulations allow visualization of the network states and detailed mechanisms of signal propagation.

Nanocatalyzed organoboron synthesis is currently a topic of significant interest as it overcomes some of the limitations of homogeneous catalyst systems. This chapter focuses on the use of nanoparticles to catalyze carbon–boron bond-formation reactions via different approaches including diboration and hydroboration of C–C multiple bonds as well as C–H and C–X (X = Br, I) borylation reactions.

Electrical signals in networks of nanoparticles emulate correlated avalanches of signals and criticality in the brain., Current efforts to achieve neuromorphic computation are focused on highly organized architectures, such as integrated circuits and regular arrays of memristors, which lack the complex interconnectivity of the brain and so are unable to exhibit brain-like dynamics. New architectures are required, both to emulate the complexity of the brain and to achieve critical dynamics and consequent maximal computational performance. We show here that electrical signals from self-organized networks of nanoparticles exhibit brain-like spatiotemporal correlations and criticality when fabricated at a percolating phase transition. Specifically, the sizes and durations of avalanches of switching events are power law distributed, and the power law exponents satisfy rigorous criteria for criticality. These signals are therefore qualitatively and quantitatively similar to those measured in the cortex. Our self-organized networks provide a low-cost platform for computational approaches that rely on spatiotemporal correlations, such as reservoir computing, and are an important step toward creating neuromorphic device architectures.

Nature inspired neuromorphic architectures are being explored as an alternative to imminent limitations of conventional complementary metal-oxide semiconductor (CMOS) architectures. Utilization of such architectures for practical applications like advanced pattern recognition tasks will require synaptic connections that are both reconfigurable and stable. Here, we report realization of stable atomic-switch networks (ASN), with inherent complex connectivity, self-assembled from percolating metal nanoparticles (NPs). The device conductance reflects the configuration of synapses which can be modulated via voltage stimulus. By controlling Relative Humidity (RH) and oxygen partial-pressure during NP deposition we obtain stochastic conductance switching that is stable over several months. Detailed characterization reveals signatures of electric-field induced atomic-wire formation within the tunnel-gaps of the oxidized percolating network. Finally we show that the synaptic structure can be reconfigured by stimulating at different repetition rates, which can be utilized as short-term to long-term memory conversion. This demonstration of stable stochastic switching in ASNs provides a promising route to hardware implementation of biological neuronal models and, as an example, we highlight possible applications in Reservoir Computing (RC)., Comment: 12 Pages, 8 Figures

The relationship between structure and physical properties such as magnetic moment and Curie temperature is studied theoretically for the recently synthesized equiatomic quaternary Heusler alloy CuNiMnSb, which is found to crystallize in the LiMgPdSb structure. Calculations are performed for various different possible structural phases within the framework of the D03-type structure (space group F 4 ¯ 3 m ) by changing the sequence of the atoms along the body diagonal of fcc lattice that characterizes the structure of this alloy. Total energy, magnetic moment and the Curie temperature results, in particular the latter two, suggest that the correct order of the atoms along the body diagonal is most likely Ni(0,0,0), Mn(0.25,0.25,0.25), Cu(0.5,0.5,0.5) and Sb(0.75,0.75,0.75) in contrast to (disagreement with) the conclusions of a recent experimental study. Neither the sequence Ni-Cu-Mn-Sb nor Ni-Mn-Cu-Sb shows a large spin polarization at the Fermi level.

We report results of a first-principles density-functional study of alloys of the 4 d -element Mo with group IV elements Si, Ge and Sn in zinc blende (ZB) and rock salt (RS) structures. The study was motivated by a similar study of ours based on the 4 d -element Tc, which showed the presence of half-metallic states with integer magnetic moment ( 1 μ B ) per formula unit in TcX (X=C, Si, Ge) alloys. The calculated Curie temperatures for the ferromagnetic (FM) phases were low, around or less than 300 K. Searching for the possibility of 4 d -based alloys with higher Curie temperatures we have carried out the study involving the elements Mo, Ru and Rh. Among these the most promising case appears to be that involving the element Mo. Among the MoX (X=Si, Ge, Sn) alloys in ZB and RS structures, both MoGe and MoSn in ZB structures are found to possess an integer magnetic moment of 2 μ B per formula unit. ZB MoSn can be classified as a marginal/weak half-metal or a spin gapless semiconductor, while ZB MoGe would be best described as a gapless magnetic semiconductor. The calculated Curie temperatures are in the range 300–700 K. Considering the theoretical uncertainty in the band gaps due not only to the treatment of exchange and correlation effects, but density functional theory itself, these classifications may change somewhat, but both merit investigation from the viewpoint of potential spintronic application. Based on their higher Curie temperatures, Mo-based alloys would serve such purpose better than the previously reported Tc-based ones.

Biological neuronal networks are the computing engines of the mammalian brain. These networks exhibit structural characteristics such as hierarchical architectures, small-world attributes, and scale-free topologies, providing the basis for the emergence of rich temporal characteristics such as scale-free dynamics and long-range temporal correlations. Devices that have both the topological and the temporal features of a neuronal network would be a significant step toward constructing a neuromorphic system that can emulate the computational ability and energy efficiency of the human brain. Here we use numerical simulations to show that percolating networks of nanoparticles exhibit structural properties that are reminiscent of biological neuronal networks, and then show experimentally that stimulation of percolating networks by an external voltage stimulus produces temporal dynamics that are self-similar, follow power-law scaling, and exhibit long-range temporal correlations. These results are expected to have important implications for the development of neuromorphic devices, especially for those based on the concept of reservoir computing., Author Summary Biological neuronal networks exhibit well-defined properties such as hierarchical structures and scale-free topologies, as well as a high degree of local clustering and short path lengths between nodes. These structural properties are intimately connected to the observed long-range temporal correlations in the network dynamics. Fabrication of artificial networks with similar structural properties would facilitate brain-like (“neuromorphic”) computing. Here we show experimentally that percolating networks of nanoparticles exhibit similar long-range temporal correlations to those of biological neuronal networks and use simulations to demonstrate that the dynamics arise from an underlying scale-free network architecture. We discuss similarities between the biological and percolating systems and highlight the potential for the percolating networks to be used in neuromorphic computing applications.

This cross sectional descriptive study was performed on 70 postmortem vermiform appendices (male 34 and female 36) to find out the various positions of vermiform appendix of Bangladeshi people. The specimens were collected from autopsy laboratory of the Department of Forensic Medicine, Mymensingh Medical College, Mymensingh, Bangladesh by purposive sampling technique from October 2016 to March 2017. The collected samples were divided into four age groups. They were Group A (upto 20 years), Group B (21 to 40 years), Group C (41 to 60 years) and Group D (above 60 years). Dissection was performed according to standard autopsy technique. During postmortem examination abdominal cavity was routinely exposed by classical midline incision from xiphoid process to the symphysis pubis and a semicircular incision around the umbilicus and the flaps were reflected to give a good view of the abdominal cavity along with its contents and then the taeniae coli of the caecum were identified. The three taeniae coli of the caecum converge at the base of the appendix and become its longitudinal muscle coat. The anterior caecal taeniae coli acts as the best guide for identification of the vermiform appendix. The relation of the base of the appendix to the caecum is constant but the position of the vermiform appendix, which is variable, was studied in relation to caecum and the terminal part of the ileum. Accordingly the position of the vermiform appendix was noted either retrocaecal, pelvic, preileal or postileal, subcaecal. All data were recorded in the predesigned data sheet, analyzed by SPSS program (version 21, 2012) and compared with the findings of other national and international studies and standard text books. Among 70 specimens, 44(62.9%) vermiform appendices were retrocaecal in position. The next common position was pelvic which was in 22(31.4%) specimen followed by postileal in 3(4.3%) specimen and subcaecal was observed only in 1(1.4%) specimen. In this study in all age groups incidence of retrocaecal vermiform appendix was highest and it was about 67.6%, 50%, 69.2% and 72.7% in Group A, B, C, D respectively. Pelvic position was 7.1%, 46.9%, 23.1% and 27.3% in Group A, B, C, D respectively. Subcaecal vermiform appendix was absent in Group A, B and Group D. On the other hand postileal vermiform appendix was absent in Group C and Group D. The findings of this study may help the physician and the surgeons for proper diagnosis, management and treatment of disease of vermiform appendix.

We report a detailed study of neuromorphic switching behaviour in inherently complex percolating networks of self-assembled metal nanoparticles. We show that variation of the strength and duration of the electric field applied to this network of synapse-like atomic switches allows us to control the switching dynamics. Switching is observed for voltages above a well-defined threshold, with higher voltages leading to increased switching rates. We demonstrate two behavioral archetypes and show how the switching dynamics change as a function of duration and amplitude of the voltage stimulus. We show that the state of each synapse can influence the activity of the other synapses, leading to complex switching dynamics. We further demonstrate the influence of the morphology of the network on the measured device properties, and the constraints imposed by the overall network conductance. The correlated switching dynamics, device stability over long periods, and the simplicity of the device fabrication provide an attractive pathway to practical implementation of on-chip neuromorphic computing.

The inherent power of the biological brain, with regard to pattern recognition, is unparalleled and cannot even be matched by multi-million dollar supercomputers. Inspired from this, neuromorphic computation, where ideas originating from the complex structure and functionality of the biological brain are utilized for advanced computation has shown great potential. In this regard, we are developing on-chip pattern classification capabilities via inexpensive self-assembly of nanoparticles (NPs). The formation of percolating microstructure of Sn NPs and tunnel junctions leads to a complex atomic-switch network (ASN) poised near criticality. Voltage stimulation is utilized for modulating the synaptic structure of the network, which shows potential for utilization as a ‘reservoir’ in reservoir computing (RC).

The electronic and galvanomagnetic properties of the equiatomic quaternary Heusler alloy CoMnFeSi, which was recently synthesized and which crystallizes in the cubic LiMgPdSb structure, are studied from first principles. We concentrate on two problems: (i) the origin of the alloy disorder, which was found to exist in this alloy, and (ii) the evaluation of basic galvanomagnetic properties such as the dc conductivity ${\ensuremath{\sigma}}_{\mathrm{tot}}$ and the anomalous Hall conductivity(AHC) for swap defects, accompanied by a comparison of the calculated results with a recent experiment. The origin of the alloy disorder is investigated by estimating corresponding formation energies of possible swap defects which preserve the sample stoichiometry. We discuss various defects with respect to the sample half metallicity. The most favorable swap types are those for which the calculated ${\ensuremath{\sigma}}_{\mathrm{tot}}$ and AHC agree reasonably with the experiment. On the basis of calculated transport quantities ${\ensuremath{\sigma}}_{\mathrm{tot}}$ (AHC), the two most favorable swap types can be identified, namely, (i) the Co-Fe swaps, which preserve the half metallicity and have the lowest formation energy, and (ii) the Co-Mn swaps, which violate the half metallicity but have larger formation energy.

Most research explains underpricing of initial public offerings (IPOs) as the rational response of investors to the valuation uncertainty and the existence of informational friction in the IPO market. In contrast, Miller (1977) demonstrates that irrational sentiments of optimistic investors lead to high underpricing which pessimistic investors are unable to correct due to short selling constraints. Using first day flipping ratio and the trading ratio as proxies for divergence of opinion, we provide evidence consistent with Miller (1977) from Indian market that the greater divergence of opinion among investors results into higher underpricing. Previous research is not unanimous on proxies for short selling constraints and also do not control for the cross-sectional differences in the severity of constraints. We test Miller’s hypothesis in a market that faced prohibitive regulatory restrictions on short selling. We also control for the period when constraints are marginally relaxed. Our findings provide more robust evidence. Our results suggest that short selling restrictions affect market efficiency adversely; there could still be other forces at play. Market regulators should take steps to facilitate short selling instead of restricting it.

Three potentials of the Finnis–Sinclair type are studied with regard to their suitability for predicting bulk thermal and elastic properties of fcc metals Cu, Ag, Au and Pt over a wide temperature range. We start with a particular parametrization of the Finnis–Sinclair model known as the Sutton–Chen potential and a later version of the same, known as the quantum Sutton–Chen potential. The quasiharmonic lattice dynamics method is used to study the temperature variation of the thermodynamic properties. Both models are found to yield poor results for thermal expansion, which can be traced to rapid softening of transverse phonon frequencies with increasing lattice parameter. The form of the Sutton–Chen potential is modified here to seek improvement in the agreement between quasiharmonic calculations and experimental data. It is found that the modified potential better predicts bulk properties in nearly all cases studied. Significant improvement is seen over the Sutton–Chen potential, while lesser but still substantial improvement is observed over the Quantum-Sutton Chen potential.

Two groups of effective pair-potentials are studied from the viewpoint of their suitability in being able to describe solid state properties and liquid state structure of noble metals Cu, Ag and Au over a wide temperature range. Since the effective pair-potentials are usually empirical in nature, with parameters obtained by fitting to some reference state properties, the objective of the present study is to determine whether a particular parametrization scheme has any definite advantage over another. We consider Morse potentials with parameters determined by equilibrium lattice parameter, cohesive/sublimation energies as well as bulk modulus values of the solid at low/room temperatures. The other group of potentials considered is Erkoc potentials, where the parameters were determined first by studying dimers and further modified using bulk stability condition and bulk cohesive energy values. The potentials were then used to study the energetics of microclusters containing 3–7 atoms. Quasiharmonic results for the solid obtained at different temperatures and Monte Carlo simulation for the liquid state show that phonon spectra, thermal expansion, temperature-dependence of specific heats and liquid structure are much better described by the latter group. The first group of potentials may have an advantage in reproducing the temperature-dependence of elastic constants and bulk moduli, since they are based on room temperature values of these properties, which show only weak temperature-dependence in general for all metals. It is argued that potentials based on parameters fitted to the properties at a single volume are less versatile in capturing the temperature-dependence of various thermodynamic properties over a wide range. Potentials capable of reproducing the energetics of clusters of different co-ordination numbers and volumes per atom may fare better in this regard.

This work presents the results for the magnetic properties of the compound SnTe doped with 3 d transition metal Mn from the viewpoint of potential application in spintronics. We report a systematic density-functional study of the electronic structure and magnetic properties of these ternary compounds in both rock salt and zinc blende structures. In both cases, it is the Sn-sublattice that is doped with Mn. Among the various compounds studied, we identify one as a possible half-metallic candidate: 25% Mn-doping of the Sn-sublattice in the rock salt structure. Others are either magnetic semiconductors or metals. Exchange interaction between the Mn atoms is discussed and results for resistivities for various compositions in the two structures are compared. For low Mn concentration, the zero temperature ground state of the compound is found to be semiconducting and the Mn–Mn exchange interactions are dominantly antiferromagnetic. The weakly ferromagnetic interaction and ordering found in experiments is shown to be ‘carrier induced’. It is shown that ferromagnetic interactions between the Mn atoms are caused by the presence of ‘holes’. Another likely cause is the presence of extra Te atoms in interstitial locations, which seems to suppress Mn–Mn antiferromagnetic interactions. This is supported by the earlier experimental observation that a weak ferromagnetism occurs in these alloys for low Mn concentration only if the samples are subjected to additional Te-flux.

We report results of a first-principles density-functional study of three binary transition-metal compounds TcX (X=C, Si and Ge) in the hypothetical cubic zinc blende (ZB) structure. Our calculations are based on the full potential linear augmented plane wave (FP-LAPW) plus local orbitals method, together with generalized gradient approximation for the exchange-correlation potential. Half-metallic (HM) ferromagnetism is observed in these binary compounds for their optimized cell volumes. In the HM state, these compounds possess an integer magnetic moment ( 1.000 μ B ) per formula unit, which is one of the important characteristics of half-metallic ferromagnets (HMFs). The ferromagnetic (FM) state is found to be stable for ZB TcC, TcSi and TcGe against the nonmagnetic (NM) and antiferromagnetic (AFM) states. Calculations show that half-metallicity can be maintained for a wide range of lattice constants in these binary compounds. Density functional calculations of exchange interactions and the Curie temperatures reveal similar trends for the three compounds with respect to the lattice parameter. These compounds are compatible with the traditional semiconductors, and could be useful in spin-electronics and other applications. The most important aspect of this work is to explore the possibility of not only magnetism, but HM ferromagnetism in compounds involving NM elements and 4 d transition element Tc.

2 MeV protons and 1 MeV carbon ions are bombarded on highly oriented pyrolytic graphite (HOPG) samples and their electronic transport measurements are carried out in the presence of magnetic field. The Magneto-Resistance (MR) measurements show measurable hysteresis in the resistance value after ion beam irradiation for the in-plane magnetic field direction as well as for the out-of-plane field direction. The MR depends on the thickness of the flake and the method of its separation from the bulk HOPG. The results substantiate that the ferromagnetic coupling between the magnetic moments at the vacancy defect sites in HOPG sensitively depends on the average defect separation. The average defect separation range of 1.7–0.5 nm allows only a part of the 40 μm thick proton beam irradiated sample to go for ferromagnetic ordering. Similar conclusions are drawn from carbon ion irradiated HOPG flake. The irradiation increases the resistance of the flake as well.

We present results of the exchange interactions and Curie temperatures in some Cr-based chalcogenides and pnictides. The calculations are performed mostly for Zinc Blende (ZB) structure with the lattice parameter varying between 5.45 and 6.6 Å, appropriate for some typical II-VI and III-V semiconducting substrates. Electronic structure is calculated via the linear muffintin-orbitals method and disorder effects, when appropriate, are taken into account via the coherent potential approximation. Calculated exchange interactions are used to estimate the Curie temperature by employing the mean-field and the random phase approximations. For CrTe we compare the results of the ZB and Rock-Salt (RS) structures.

The electronic properties, exchange interactions, Curie temperatures and transport properties of random quaternary Heusler alloys (Ni, Cu)2MnSn are studied by means of density-functional calculations over the entire range of dopant concentration. Results agree qualitatively as well as quantitatively with the available experimental data. The residual resistivity is found to obey the Nordheim rule, indicating weak-scattering regime. The temperature-dependent spin-disorder resistivity is found to be described well via the disordered model of local moments. Effect of pressure on the Curie temperature and the resistivity is also explored.

Malls came into existence because of changing patterns of urbanization and ways of living. The concept has traveled from the United States to the world over. Initially, the acceptance and awareness of malls was moderate in India, but there has been a spur in the proliferation of malls during recently. Indian malls are not an exact replica of the U.S. malls: the U.S. model has been modified resulting in development of India-specific prototypes. Indian malls differ from U.S. malls in terms of financing, location, size, expansion, architecture, stage of evolution, choice of anchor tenant, entertainment-mix, and mall management practices.

This work provides the first systematic test of validity of the embedded-atom potentials of Mei et al. [Phys. Rev. B 43 (1991) 4653], via a complete study of the vibrational and thermodynamic properties of isoelectronic transition (Ni, Pd, Pt) and noble (Cu, Ag, Au) metals. Phonon dispersion curves and thermal properties are studied within the quasiharmonic approximation. Results for the temperature-dependence of the lattice constants, coefficients of linear thermal expansion, isothermal and adiabatic bulk moduli, heat capacities at constant volume and constant pressure, Debye temperatures and Gruneisen parameters are presented. Electronic contribution to the specific heat is included explicitly via density-functional calculation. The calculated phonon frequencies for Ag and Cu agree well with the results from inelastic neutron scattering experiments. Despite less satisfactory agreement between calculated and measured phonon frequencies for the other four metals, isothermal and adiabatic bulk moduli and the specific heats of all metals are reproduced reasonably well by the model, while the Gruneisen parameter and Debye temperature are underestimated by about 10%. The coefficient of linear thermal expansion is underestimated with respect to measured values in most cases except for Pt and Au. The results are good for Pt up to 1000 K and for Au up to 500 K.

To begin with, it would be appropriate to note definitions of the two terms, ‘Corporate governance’ and ‘Risk management’. Organization for Economic Cooperation & Development defines ‘Corporate Governance’ as a ‘set of relationship between company's management, its board, its shareholders and other stakeholders. Corporate governance also provides the structure through which the objectives of the company are determined. Good corporate governance should provide proper incentives for the board and management to pursue objectives that are in the interest of the company and its shareholders/stakeholders and should facilitate effective monitoring, thereby encouraging firms to use resources more effectively. ‘Risk management’, on the other hand, is defined as the identification, analysis and economic control of all such risks that may threaten assets, resources, or earning capacity of a firm/company. Risk management is in reality ‘an all business activities embracing’ tool and with a high standard of risk management, it would naturally be possible to ensure high standard of corporate governance. The close relationship between corporate governance and risk management can thus be easily understood.

Natural computers exploit the emergent properties and massive parallelism of interconnected networks of locally active components. Evolution has resulted in systems that compute quickly and that use energy efficiently, utilizing whatever physical properties are exploitable. Man-made computers, on the other hand, are based on circuits of functional units that follow given design rules. Hence, potentially exploitable physical processes, such as capacitive crosstalk, to solve a problem are left out. Until now, designless nanoscale networks of inanimate matter that exhibit robust computational functionality had not been realized. Here we artificially evolve the electrical properties of a disordered nanomaterials system (by optimizing the values of control voltages using a genetic algorithm) to perform computational tasks reconfigurably. We exploit the rich behaviour that emerges from interconnected metal nanoparticles, which act as strongly nonlinear single-electron transistors, and find that this nanoscale architecture can be configured in situ into any Boolean logic gate. This universal, reconfigurable gate would require about ten transistors in a conventional circuit. Our system meets the criteria for the physical realization of (cellular) neural networks: universality (arbitrary Boolean functions), compactness, robustness and evolvability, which implies scalability to perform more advanced tasks. Our evolutionary approach works around device-to-device variations and the accompanying uncertainties in performance. Moreover, it bears a great potential for more energy-efficient computation, and for solving problems that are very hard to tackle in conventional architectures.

The electronic structure of a modified version of the Quandt–Elser model of i-Al70.8Pd21.5Mn7.7 is studied by the full-potential linearized augmented plane wave method. Inspection of the electronic charge density and an analysis based on Bader's concept of atoms in a molecule reveal a charge transfer from the Al atoms to Mn. It is argued that this charge transfer is responsible for the negative valence of Mn in i-Al–Pd–Mn quasicrystals.

We present a variational study of the helicity moduli of an anisotropic quantum three-dimensional (3D) XY-model of YBCO in superconducting state. It is found that both the ab-plane and the c-axis helicity moduli, which are proportional to the inverse square of the corresponding magnetic field penetration depth, vary with temperature T as T to the fourth power in the zero temperature limit. Moreover, the c-axis helicity modulus drops with temperature much faster than the ab-plane helicity modulus because of the weaker Josephson couplings along the c-axis compared to those along the ab-plane. These findings are in disagreement with the experiments on high quality samples of YBCO.

We present a Monte Carlo study of the helicity moduli of an anisotropic classical three-dimensional (3D) XY-model of YBCO in superconducting state. It is found that both the ab-plane and the c-axis helicity moduli, which are proportional to the inverse square of the corresponding magnetic field penetration depth, vary linearly with temperature at low temperatures. The result for the c-axis helicity modulus is in disagreement with the experiments on high quality samples of YBCO. Thus we conclude that purely classical phase fluctuations of the superconducting order parameter cannot account for the observed c-axis electrodynamics of YBCO.

We report the first direct observation of a high-moment (HM)/low-moment (LM) transition occurring in face centered cubic (FCC) Fe-Ni alloys. 57 Fe Mossbauer isomer shifts (ISs) give local electronic densities that exhibit a large discontinuity of , 0.4 el./ $ a_{0}^3 $ at the transition that spans the concentration range ∼ 65-75 apc (atomic percent) Fe, in agreement with ab initio predictions. In the most Fe-rich alloys that have LM ground states (including n -Fe), we show that thermal stabilization of the HM state occurs at high temperatures, thereby providing an experimental proof that anti-Invar behavior is due to such HM stabilization. In Invar (Fe 65 Ni 35 ) and at near-Invar compositions, we observe temperature-induced changes in electronic density that follow the spontaneous magnetization curves and find that Invar is predominantly a HM phase at all temperatures where an Invar effect occurs. We show that LM phase thermal excitation cannot cause the Invar effect and that such excitation would cause ...

The superconducting transition temperature T c of polycrystalline samples of MgB 2 was studied under hydrostatic and quasi-hydrostatic pressures up to 1 and 12 GPa, respectively. The rate of T c change with hydrostatic pressure, (d T c /d P ), was found to be −1.18 K (GPa) −1 . Quasi-hydrostatic measurements yield a slightly higher value: (d T c /d P )=−1.2 K (GPa) −1 . Analysis of the electron–phonon coupling parameter λ and its logarithmic volume derivative using the McMillan expression for T c yields results that fall within the range of a conventional s-wave BCS superconductor with intermediate coupling, in agreement with several experimental and theoretical studies that have already been reported. Based on electronic structure calculations performed by us as well as those reported in the literature, it is concluded that the change in the coupling parameter λ is dominated by the change of the average phonon frequency with pressure.

We report the first conclusive observation of a high-moment (HM)/low-moment (LM) transition occurring in face centered cubic Fe–Ni alloys. 57Fe Mossbauer isomer shifts give local electronic densities that exhibit a large discontinuity of ∼0.4 el./a03 at the transition that spans the concentration range ∼60–80 at% Fe, in agreement with ab initio predictions. Our electronic structure calculations give an isomer shift discontinuity at a comparable composition and of the same magnitude as the observed one. This identification of the HM/LM transition in Fe–Ni allows an interpretation of the compositional dependence of the lattice parameter (at room temperature or extrapolated to T=0 K) in which it is seen that the Invar effect is an expansion, relative to normal HM non-magnetovolume active behavior, not a contraction as is required in all two-γ-state-like interpretations. Indeed, the Invar effect and the HM/LM transition are seen as two distinct and competing phenomena that dominate at different compositions and that arise from different features of the electronic structure: a large inter-atomic separation dependence of the magnetic exchange interaction between large local moments versus instability of the local moment magnitude, respectively. In the Fe-rich alloys including Invar (Fe65Ni35), we observe temperature-induced changes in electronic density that follow the spontaneous magnetization curves and that are both consistent with the associated loss of local moment orientation order and inconsistent with a significant loss of local moment magnitude. This establishes that Invar is predominantly a HM phase at all temperatures where an Invar effect occurs. In the most Fe-rich alloys that have LM ground states (including γ-Fe), we find that thermal stabilization of the HM phase occurs at high temperatures (i.e., increase of local moment magnitude with increasing temperature), along a continuum of homogeneous phases between the LM and HM extremes, in a manner that is consistent with the expected local moment entropic contribution to the free energy. The latter effect, reported here for the first time, gives rise to the unusually large thermal expansion coefficients of these alloys, known as the anti-Invar phenomenon.

This work presents the results of first principles calculations of the electronic and magnetic properties of the compound SnTe and GeTe in zinc blende (ZB) and rock salt (RS) structures, doped with 3d transition metal V, Cr, and Mn. The present study, initiated from the viewpoint of potential application in spintronics, is motivated by our earlier work involving these two compounds, where the doping was limited to the Sn and Ge sublattices. In view of some discrepancies between our calculated results and the available experimental data, in this work we have examined the effect of the Te-sublattice doping. The case of Mn-doping, where the previous results of calculations seemed to differ most from the experimentally available data, is examined further by looking at the effect of Mn atoms partially occupying interstitial sites as well. From the standpoint of potential application in spintronics, we look for half-metallic (HM) states and tabulate their properties in both rock salt and zinc blende structures. ZB structure is found to be more conducive to HM state in general. Among the binary compounds we identify several HM candidates: VGe, VSn, MnGe, MnSn and MnTe at their equilibrium volumes and all in ZB structure. Estimates of the Curie temperature for the ferromagnetic compounds including the half-metals are presented. It is shown that despite the ferromagnetic (FM) nature of the Mn-Mn interaction for the Te-doped case, a simultaneous doping of both Ge(Sn)- and Te-sublattice with Mn atoms would leave the material predominantly antiferromagnetic (AFM).

We present first-principles electronic structure calculations of some face-centered-cubic disordered ternary Invar alloys, using the tight-binding linearized muffin-tin orbital method combined with the coherent-potential approximation (TB-LMTO-CPA). We calculate the total energies, equilibrium lattice parameters, bulk moduli, magnetic moments, and hyperfine fields for Fe-Ni-Co, Fe-Ni-Pd, and Fe-Ni-Pt Invar alloys. Charge densities at the nuclei, which can be used to interpret the results of isomer shift experiments in these alloys, are also presented. The effects of systematic Co, Pd, and Pt substitution in binary ${\mathrm{Fe}}_{65}{\mathrm{Ni}}_{35}$ alloy on the above properties are carefully examined. We examine the high moment to low moment transition by varying the concentration of Fe. Total-energy curves as a function of the lattice parameter show two distinct minima corresponding to the ferromagnetic (high moment and high volume) and nonmagnetic (zero moment and low volume) states. By using the Debye-Gr\"uneisen model, we calculate thermal-expansion coefficients of these alloys near the Invar compositions. The results are in qualitative agreement with the experimental trend. Finally, we present results for the effective exchange coupling parameter in these alloys following the LMTO-CPA treatment of Liechtenstein et al. [J. Magn. Magn. Mater. 67, 65 (1987)]. Comparison of the calculated quantities with available experimental results is provided, wherever appropriate and feasible.